U.S. patent application number 15/273961 was filed with the patent office on 2017-03-30 for road vehicle with an electric drive.
The applicant listed for this patent is Ferrari S.p.A. Invention is credited to Franco Cimatti.
Application Number | 20170087975 15/273961 |
Document ID | / |
Family ID | 55070025 |
Filed Date | 2017-03-30 |
United States Patent
Application |
20170087975 |
Kind Code |
A1 |
Cimatti; Franco |
March 30, 2017 |
ROAD VEHICLE WITH AN ELECTRIC DRIVE
Abstract
A road vehicle with an electric drive having: a heat engine
provided with a carrier shaft; a gearbox; at least one pump
actuated by a carrier shaft; at least a reversible electric
machine; a first mechanical transmission, which transmits the
motion from the drive shaft of the heat engine to the carrier shaft
and is provided with a first freewheel; a second mechanical
transmission, which transmits the motion from the shaft of the
electric machine to the carrier shaft and is provided with a second
freewheel; and a third mechanical transmission, which is arranged
in parallel to the second mechanical transmission, transmits the
motion from the shaft of the electric machine to the carrier shaft,
is provided with a third freewheel and reverses the direction of
motion with respect to the second mechanical transmission.
Inventors: |
Cimatti; Franco; (Pavullo,
IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ferrari S.p.A, |
Modena |
|
IT |
|
|
Family ID: |
55070025 |
Appl. No.: |
15/273961 |
Filed: |
September 23, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60K 6/48 20130101; B60K
17/26 20130101; B60Y 2400/70 20130101; F16H 2200/0013 20130101;
B60K 6/547 20130101; B60K 25/00 20130101; F16D 41/00 20130101; F16H
2003/0931 20130101; B60K 2006/4825 20130101; B60Y 2200/92 20130101;
F16H 61/30 20130101; F16H 2200/0021 20130101; Y10S 903/909
20130101; B60K 2025/005 20130101; B60K 2006/541 20130101; F16H
3/003 20130101; F16H 57/0439 20130101; F16H 3/093 20130101; F16H
61/0028 20130101; B60K 17/02 20130101; B60Y 2400/42 20130101; B60K
6/36 20130101; F16H 57/0441 20130101; B60K 25/02 20130101; F16H
2200/0056 20130101; B60K 25/06 20130101; Y02T 10/62 20130101; B60K
6/383 20130101; F16H 3/006 20130101; F16H 3/10 20130101; Y10S
903/919 20130101; B60K 6/38 20130101; Y10S 903/912 20130101 |
International
Class: |
B60K 6/547 20060101
B60K006/547; B60K 6/36 20060101 B60K006/36; F16H 61/30 20060101
F16H061/30; F16H 3/093 20060101 F16H003/093; F16H 3/10 20060101
F16H003/10; F16H 57/04 20060101 F16H057/04; B60K 6/38 20060101
B60K006/38; F16H 3/00 20060101 F16H003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2015 |
IT |
102015000054742 |
Claims
1. A road vehicle (1) with an electric drive comprising: at least
one pump (25, 26), which is operated by a carrier shaft (27); at
least one reversible electric machine (8) having a shaft (23); and
a first mechanical transmission (30), which transmits the motion
from the shaft (23) of the electric machine (8) to the carrier
shaft (27) and is provided with a first freewheel (33); the road
vehicle (1) being characterized in that it comprises a second
mechanical transmission (31), which is arranged in parallel to the
first mechanical transmission (30), transmits the motion from the
shaft (23) of the electric machine (8) to the carrier shaft (27),
is provided with a second freewheel (34) and reverses the direction
of motion if compared to the first mechanical transmission
(30).
2. A road vehicle (1) according to claim 1, wherein the first
freewheel (33) is oppositely mounted if compared to the second
freewheel (34).
3. A road vehicle (1) according to claim 1, and comprising: a heat
engine (5) provided with a drive shaft (6); and a third mechanical
transmission (28), which is designed to transmit the motion from
the drive shaft (6) of the heat engine (5) to the carrier shaft
(27) and is provided with a third freewheel (32).
4. A road vehicle (1) according to claim 3, wherein the gear ratio
determined by the third mechanical transmission (28) is different
from the gear ratio determined by the first mechanical transmission
(30) and by the second mechanical transmission (31).
5. A road vehicle (1) according to claim 3, wherein the gear ratio
determined by the third mechanical transmission (28) is higher than
the gear ratio determined by the first mechanical transmission (30)
and by the second mechanical transmission (31), so that, given the
same inlet speed, the third mechanical transmission (28) rotates
the carrier shaft (27) faster than the first mechanical
transmission (30) and the second mechanical transmission (31).
6. A road vehicle (1) according to claim 3, wherein the third
mechanical transmission (28) is made up of a train of gear wheels
and comprises a first gear wheel (35), which receives the motion
from the drive shaft (6) of the heat engine (5), and a second gear
wheel (36), which meshes with the first gear wheel (35) and is
coupled to the carrier shaft (27) through the third freewheel
(32).
7. A road vehicle (1) according to claim 6, wherein the third
freewheel (32) is built-in in the second gear wheel (36).
8. A road vehicle (1) according to claim 1, wherein the first
mechanical transmission (30) is made up of a train of gear wheels
and comprises a third gear wheel (37), which is coupled to the
carrier shaft (27), and a fourth gear wheel (38), which meshes with
the third gear wheel (37) and is coupled to the shaft (23) of the
electric machine through the first freewheel (33).
9. A road vehicle (1) according to claim 8, wherein the first
freewheel (33) is built-in in the fourth gear wheel (38).
10. A road vehicle (1) according to claim 1, wherein the second
mechanical transmission (31) is made up of a train of gear wheels
and comprises a fifth gear wheel (39), which is coupled to the
carrier shaft (27), a sixth gear wheel (40), which is coupled to
the shaft (23) of the electric machine (8) through the second
freewheel (34) and a seventh gear wheel (41), which is interposed
between the fifth gear wheel (39) and the sixth gear wheel
(40).
11. A road vehicle (1) according to claim 10, wherein the second
freewheel (34) is built-in in the sixth gear wheel (40).
12. A road vehicle (1) according to claim 1 and comprising a
circulation pump (25), which causes the circulation of a lubricant
oil and is operated by the carrier shaft (27).
13. A road vehicle (1) according to claim 1 and comprising a second
actuating pump (26), which provides the hydraulic pressure needed
for the operation of the gearbox and is operated by the carrier
shaft (27).
14. A road vehicle (1) according to claim 1, wherein the carrier
shaft (27) extends through the pump (25, 26).
Description
TECHNICAL FIELD
[0001] The present invention relates to a road vehicle with an
electric drive.
[0002] The present invention finds advantageous application in a
road vehicle with hybrid drive (i.e. both thermal and electric), to
which the following discussion will make explicit reference without
loss of generality.
PRIOR ART
[0003] A hybrid vehicle comprises an internal combustion engine,
which transmits the drive torque to the drive wheels by means of a
transmission provided with a gearbox coupled to a clutch, and at
least one electric machine, which is electrically coupled to an
electrical storage system and mechanically coupled to the driving
wheels.
[0004] The vehicle can be run by: thermal traction, wherein the
drive torque is generated only by the heat engine and possibly the
electric machine operates as a generator to recharge the electrical
storage system; electric traction, wherein the engine is off and
the drive torque is generated only by the electric machine
operating as an engine; or combined traction, wherein the drive
torque is generated both by the heat engine and by the electric
machine operating as an engine. Moreover, to increase the overall
energy efficiency, in all deceleration stages the electric machine
is used as a generator to produce a regenerative deceleration in
which the kinetic energy possessed by the vehicle, instead of being
completely dissipated in friction, is at least partly converted in
electrical energy that is stored in the electrical storage
system.
[0005] In some hybrid vehicles, the transmission comprises a
circulation pump, which allows the circulation of a lubrication oil
through the transmission gears to ensure an adequate lubrication to
the gears. In addition, in the case of a hydraulic power-assisted
(i.e. robotized) transmission, the transmission also comprises an
implementation pump that supplies the hydraulic pressure required
to operate the hydraulic actuators for engaging and selecting the
gear and controlling the clutch.
[0006] In currently produced vehicles, the transmission pumps are
driven by an auxiliary carrier shaft, which is operated by the
drive shaft (hence upstream of the clutch) to be always operated,
even when the clutch is open. This structure makes less convenient
the mechanical coupling of an electric machine to a gear shaft,
since in the case of the electric traction (i.e. when the engine is
off), the clutch must remain closed to actuate the transmission
pumps, and therefore also the heat engine is rotated (with
considerable friction and inertia).
[0007] To solve the aforesaid problem, it has been proposed that
the carrier shaft of the transmission pumps is mechanically
independent from the drive shaft and the carrier shaft of the
transmission pumps is operated by a dedicated electric motor.
However, this solution is energetically scarcely efficient, because
when the heat engine is on (i.e. for most of the time of use of the
vehicle), it is more efficient using part of the drive torque
generated by the heat engine to operate directly some auxiliary
elements rather than converting part of the drive torque generated
by the heat engine in electrical energy, which is transformed back
in mechanical torque by an electric motor. Moreover, arranging an
electric motor mechanically coupled to the carrier shaft of the
transmission pumps is not simple, since the area of the
transmission has reduced free space, is quite hot because of the
heat generated by the friction inside the clutch and the gearbox,
and is scarcely ventilated since it is normally arranged at the
centre of the vehicle.
[0008] To increase the energy efficiency in the case of the
electric traction (i.e. when the heat engine is off), the patent
applications EP2278192A1 and EP2325034A1 propose to connect the
carrier shaft of the transmission pumps both to the drive shaft, by
means of a first mechanical transmission provided with a first
freewheel, and to the shaft of the electric machine by means of a
second mechanical transmission provided with a second freewheel. In
this way, when the heat engine is on, the heat engine rotates the
carrier shaft of the transmission pumps while the electric machine
is released (thanks to the corresponding freewheel) from the
carrier shaft; on the other hand, when the heat engine is off, the
electric machine directly rotates the carrier shaft of the
transmission pumps while the engine is released (thanks to the
corresponding freewheel) from the carrier shaft.
[0009] However, the coupling system proposed in the patent
applications EP2278192A1 and EP2325034A1 allows the rotation of the
carrier shaft of the transmission pumps only when the electric
machine rotates in one direction (coinciding with the forward
motion) and not when it rotates in the opposite direction (i.e. in
reverse gear); this is disadvantageous, as it would be more
convenient to operate the reverse gear by means of the electric
traction, thus taking advantage of the complete reversibility of
the direction of rotation of the electric machine, rather than by
means of a suitable transmission gear.
DESCRIPTION OF THE INVENTION
[0010] The object of the present invention is to provide a road
vehicle with an electric drive that is free from the aforesaid
drawbacks and, at the same time, is easy and inexpensive to
produce.
[0011] According to the present invention, it is provided a road
vehicle with an electric drive as claimed in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will now be described with reference
to the accompanying drawings, showing a non-limiting embodiment,
wherein:
[0013] FIG. 1 is a schematic view of a road vehicle with hybrid
propulsion manufactured in accordance with the present
invention;
[0014] FIG. 2 is a schematic view of a transmission of the road
vehicle of FIG. 1; and
[0015] FIGS. 3 and 4 are two different schematic views of part of
the transmission of FIG. 2.
PREFERRED EMBODIMENTS OF THE INVENTION
[0016] In FIG. 1, number 1 indicates as a whole a road vehicle with
hybrid propulsion provided with two front wheels 2 and with two
rear driving wheels 3, which receive the driving torque by a hybrid
powertrain system 4.
[0017] The hybrid powertrain system 4 comprises an internal
combustion engine 5, which is arranged in a front position and is
provided with a crankshaft 6, a hydraulic power-assisted (i.e.
robotized) transmission 7, which transmits the drive torque
generated by the internal combustion engine 5 to the rear driving
wheels 3, and an electric reversible machine 8 (namely operated
both as an electric motor by absorbing electricity and generating a
mechanical drive torque and as and electrical generator by
absorbing mechanical energy and generating electricity), which is
mechanically coupled to the transmission 7.
[0018] The transmission 7 comprises a transmission shaft 9, which
on the one side is angularly integral with the drive shaft 6 and on
the other side is mechanically coupled to a dual-clutch gearbox 10,
which is arranged in the rear position and transmits the motion to
the rear driving wheels 3 by means of two axle shafts 11 receiving
the motion from a differential 12. The electric reversible machine
8 is mechanically coupled to the dual-clutch gearbox 10, as it will
be better described in the following, and is driven by an
electronic power converter 13 coupled to a storage system 14, which
stores electrical energy and is provided with chemical batteries
and/or supercapacitors.
[0019] As shown in FIG. 2, the dual-clutch gearbox 10 comprises two
primary shafts 15 and 16 which are mutually coaxial, independent
and inserted one in the other, and two clutches 17 and 18, which
are coaxial and arranged in series, each of which connects a
relative primary shaft 15 or 16 to the transmission shaft 9 (and
therefore to the drive shaft 6 of the internal combustion engine
5). Moreover, the dual-clutch gearbox 10 comprises two secondary
shafts 19 and 20, which are both angularly integral to the inlet of
the differential 11 that transmits the motion to the rear driving
wheels 3.
[0020] The dual-clutch gearbox 10 shown in FIG. 2 has seven forward
gears indicated with Roman numerals (first gear I, second gear II,
third gear III, fourth gear IV, fifth gear V, sixth gear VI and
seventh gear VII) and lacks a reverse gear (where the reverse
motion occurs by electric traction, exploiting the perfect rotation
bi-directionality of the electric machine 8); in other words, the
electric machine 8 works as a motor, with a direction of rotation
opposite to the usual, to apply to the rear driving wheels 3 a
drive torque pushing the vehicle 1 in reverse motion. The primary
shafts 15 and 16 are mechanically coupled to the secondary shafts
19 and 20 by means of a plurality of pairs of gears 21, each of
which defines a respective gear and comprises a primary gear
mounted on a primary shaft 15 or 16 and a secondary gear mounted on
a secondary shaft 19 or 20 and meshes permanently with the primary
gear. To allow the correct operation of the dual-clutch gearbox 10,
all the odd gears (first gear I, third gear III, fifth gear V,
seventh gear VII) are coupled to the same primary shaft 15, while
all the even gears (second gear II, fourth gear IV and sixth gear
VI) are coupled to the other primary shaft 16.
[0021] Each primary gear is fitted to a respective primary shaft 15
or 16 to always rotate integrally with the primary shaft 15 or 16
and meshes permanently with the respective secondary gear; instead,
each secondary gear is idly mounted on its secondary shaft 19 or
20. The dual-clutch gearbox 10 comprises for each pair of gears 21
a corresponding synchronizer 22, which is mounted coaxially to the
corresponding secondary shaft 19 or 20 and can be actuated to
engage the respective secondary gear to the secondary shaft 19 or
20 (i.e. to make the respective secondary gear angularly integral
with the secondary shaft 19 or 20).
[0022] The electric machine 8 has a shaft 23, which is permanently
coupled to the primary shaft 15 to always rotate integrally with
the primary shaft 15. According to a preferred embodiment, starting
from an existing dual-clutch gearbox 10, not initially designed for
the hybrid drive, the primary shaft 15 is extended on the opposite
side with respect to the clutches 17 and 18 so as to protrude from
a gearbox 24; then, out of the gearbox 24, the primary shaft 15 is
made angularly integral (e.g. by means of a head-to-head coupling)
with the shaft 23 of the electric machine 8.
[0023] The dual-clutch gearbox 10 comprises a circulation pump 25,
which allows the circulation of a lubricant oil through the
transmission gears 10 to ensure an adequate lubrication and an
adequate cooling of the gears. Moreover, the dual-clutch gearbox 10
comprises an actuating pump 26 that supplies the hydraulic pressure
required to operate the hydraulic actuators for engaging the gears
(i.e. the actuators of the synchronizers 22) and the control
actuators of the clutches 17 and 18.
[0024] The two pumps 25 and 26 of the gearbox 10 are actuated by an
auxiliary carrier shaft 27 (i.e. passing through each pump 25 and
26), which on the one hand takes the motion through a mechanical
transmission 28 from a front basket 29 of the clutches 17 and 18
which is angularly integral with the drive shaft 6, and on the
other hand takes the motion through two different mechanical
transmissions 30 and 31 from the primary shaft 15, which is
angularly integral with the shaft 23 of the electric machine 8. The
carrier shaft 27 must always rotate in the same direction, as the
pumps 25 and 26 may operate correctly (i.e. may pump) by rotating
only in a predetermined direction.
[0025] The mechanical transmission 28 is preferably made up of a
train of gear wheels and is provided with a freewheel 32 (or idle
wheel 32) that transmits or does not transmit the motion (i.e.
meshes or not meshes) depending on the direction of the speed
difference. The mechanical transmission 30 is preferably made up of
a train of gear wheels and is provided with a freewheel 33 (or idle
wheel 33) that transmits or does not transmit the motion (i.e.
meshes or not meshes) depending on the direction of the speed
difference. The mechanical transmission 31 is preferably made up of
a train of gear wheels and is provided with a freewheel 34 (or idle
wheel 34) that transmits or does not transmit the motion (i.e.
meshes or not meshes) depending on the direction of the speed
difference and is mounted oppositely with respect to the freewheel
33 (i.e. in an opposite meshing direction if compared to the
freewheel 33); in other words, the freewheel 34 transmits the
motion (i.e. meshes) when it rotates in a certain direction,
whereas the freewheel 33 transmits the motion (i.e. meshes) when it
rotates in the opposite direction.
[0026] The two mechanical transmissions 30 and 31 are mutually
parallel (i.e. both take their motion from the primary shaft 15,
which is angularly integral with the shaft 23 of the electric
machine 8, and transmit the motion to the auxiliary carrier shaft
27) and differ for the different (opposite) meshing direction of
the respective freewheels 33 and 34 and because the one reverses
the direction of motion with respect to the other (i.e. if the
primary shaft 15 rotates counterclockwise, the mechanical
transmission 30 rotates the auxiliary carrier shaft 27
counterclockwise, whereas the mechanical transmission 31 rotates
the auxiliary carrier shaft 27 clockwise).
[0027] Finally, the two mechanical transmissions 30 and 31 have the
same gear ratio (or anyway similar gear ratios), while the gear
ratio of the mechanical transmission 28 is higher than the gear
ratio of the mechanical transmissions 30 and 31 so that at an equal
inlet speed, the mechanical transmission 28 rotates the carrier
shaft 27 faster than the mechanical transmissions 30 and 31.
[0028] According to a possible embodiment, along the carrier shaft
27 and upstream of the mechanical transmissions 30 and 31 it is
interposed an uncoupling sleeve (not shown), which allows an axial
sliding of the portion of the carrier shaft 27 arranged to the
right of the uncoupling sleeve with respect to the portion of the
carrier shaft 27 arranged to the left of the uncoupling sleeve. The
purpose of the uncoupling sleeve is to allow the axial adjustment
of the mechanical transmissions 30 and 31 (typically to regain the
construction tolerances in the assembling phase) without affecting
the pumps 25 and 26 and the mechanical transmissions 30 and 31.
[0029] As shown in FIGS. 3 and 4, the mechanical transmission 28 is
made up of a train of gear wheels and comprises a gear wheel 35
integral with the front basket 29 of the clutches 17 and 18 (i.e.
angularly integral with the drive shaft 6 of the heat engine 5) and
a gear wheel 36 which meshes with the gear wheel 35 and is coupled
to the carrier shaft 27 through the freewheel 32; in particular,
the freewheel 32 is integrated in the gear wheel 36, i.e. forms the
hub of the gear wheel 36. The mechanical transmission 30 is made up
of a train of gear wheels and comprises a gear wheel 37 integral
with the carrier shaft 27 and a gear wheel 38 which meshes with the
gear wheel 37 and is coupled to the primary shaft 15 (i.e. to the
shaft 23 of the electric machine 8) through the freewheel 33; in
particular, the freewheel 33 is integrated in the gear wheel 38,
i.e. forms the hub of the gear wheel 38. The mechanical
transmission 31 is made up of a train of gear wheels and comprises
a gear wheel 39 integral with the carrier shaft 27, a gear wheel 40
which is coupled to the primary shaft 15 (i.e. to the shaft 23 of
the electric machine 8) through the freewheel 34, and a further
gear wheel 41 that is interposed between the gear wheels 39 and 40
and then meshes on the one side with the gear wheel 39 and on the
opposite side with the gear wheel 40; in particular, the freewheel
34 is integrated in the gear wheel 40, i.e. forms the hub of the
gear wheel 40.
[0030] Thanks to the presence of the gear wheel 41, the mechanical
transmission 31 reverses the direction of motion with respect to
the mechanical transmission 30; accordingly, if the primary shaft
15 (i.e. the shaft 23 of the electric machine 8) rotates
counterclockwise, the mechanical transmission 30 rotates the
auxiliary carrier shaft 27 counterclockwise, whereas the mechanical
transmission 31 rotates the auxiliary carrier shaft 27
clockwise.
[0031] Hereinafter a description of the operation of the
transmission 7 with reference to the implementation of the pumps 25
and 26 of the gearbox 10.
[0032] When the speed of rotation imparted to the carrier shaft 27
by the mechanical transmission 28 (and therefore by the drive shaft
6 of the heat engine 5) is higher than the speed of rotation
imparted to the carrier shaft 27 by the mechanical transmissions 30
and 31 (and therefore by the primary shaft 15 integral with the
electric machine 8), then the freewheel 32 meshes and then
transmits the motion to the pumps 25 and 26 of the gearbox 10,
while the freewheels 33 and 34 are not engaged and therefore do not
transmit the motion to the pumps 25 and 26 of the gearbox 10; in
other words, the carrier shaft 27 is rotated by the drive shaft 6
of the heat engine 5, while the carrier shaft 27 is isolated from
the primary shaft 15 integral with the shaft 23 of the electric
machine 8. The speed of rotation imparted to the carrier shaft 27
by the mechanical transmission 28 (and therefore by the drive shaft
6 of the heat engine 5) is always higher than the speed of rotation
imparted to the carrier shaft 27 by the mechanical transmissions 30
and 31 (and therefore by the primary shaft 15 integral with the
electric machine 8) when the heat engine 5 is on for advancing the
vehicle, since the gear ratio of the mechanical transmission 28 is
higher than the gear ratio of the mechanical transmissions 30 and
31.
[0033] When the speed of rotation imparted to the carrier shaft 27
by the mechanical transmission 28 (and therefore by the drive shaft
6 of the heat engine 5) is lower than the speed of rotation
imparted to the carrier shaft 27 by the mechanical transmissions 30
and 31 (and therefore by the primary shaft 15 integral with the
electric machine 8), then only one of the two freewheels 33 and 34
meshes and then transmits the motion to the pumps 25 and 26 of the
gearbox 10, while the freewheel 32 is not engaged and therefore
does not transmit the motion to the pumps 25 and 26 of the gearbox
10 (this almost always occurs only when the heat engine 5 is off
during the start/stop phase); in other words, the carrier shaft 27
is rotated by the primary shaft 15 integral with the shaft 23 of
the electric machine 8, while the carrier shaft 27 is isolated from
the drive shaft 6 of the heat engine 5.
[0034] In particular, if the primary shaft 15 integral with the
shaft 23 of the electric machine 8 rotates in one direction (when
the electric machine 8 is used for the forward motion of the road
vehicle 1), then it engages the freewheel 33 and does not engage
the freewheel 34 (i.e. the carrier shaft 27 is rotated through the
mechanical transmission 30), while if the primary shaft 15 integral
to the shaft 23 of the electric machine 8 rotates in the opposite
direction (when the electric machine 8 is used for the reverse
motion of the road vehicle 1), then it engages the freewheel 34 and
does not engage the freewheel 33 (i.e. the carrier shaft 27 is
rotated through the mechanical transmission 31); in any case, the
carrier shaft 27 always rotates in the same direction regardless of
the direction of rotation of the primary shaft 15 integral with the
shaft 23 of the electric machine 8, since the two mechanical
transmissions 30 and 31 reverse the direction of motion with
respect to one another.
[0035] In use, when the heat engine 5 is on, i.e. the drive shaft 6
of the heat engine 5 rotates and one of the clutches 17 and 18 is
closed, the speed of rotation imparted to the carrier shaft 27 by
the mechanical transmission 28 (and therefore by the drive shaft 6
of the heat engine 5) is always higher than the speed of rotation
imparted to the carrier shaft 27 by the mechanical transmissions 30
and 31 (and therefore by the primary shaft 15 integral with the
shaft 23 of the electric machine 8), since the gear ratio
determined by the mechanical transmission 28 is higher than the
gear ratio determined by the mechanical transmissions 30 and 31. In
this case, the carrier shaft 27 is rotated by the drive shaft 6 of
the heat engine 5.
[0036] When the heat engine 5 is on, i.e. the drive shaft 6 of the
heat engine 5 rotates, and the clutches 17 and 18 are both open,
the carrier shaft 27 can be rotated by the drive shaft 6 of the
heat engine 5 or can be rotated by the primary shaft 15 integral
with the shaft 23 of the electric machine 8 depending on the speed
of rotation of the shaft 23 of the electric machine 8 (i.e. of the
primary shaft 15 of the gearbox). In fact, since both clutches 17
and 18 are open, the speed of rotation of the primary shaft 15 of
the gearbox is completely independent from the rotational speed of
the drive shaft 6 of the heat engine 5. In any case, when the heat
engine 5 is on, the carrier shaft 27 is preferably rotated by the
drive shaft 6 of the heat engine 5; generally, when the heat engine
5 is on, the carrier shaft 27 is rotated by the primary shaft 15
integral with the electric machine 8 only in the case of a
regenerative braking, when the electric machine 8 works as a
generator to recover the kinetic energy of the vehicle 1.
[0037] When the heat engine 5 is off, i.e. when the drive shaft 6
of the heat engine 5 is stationary and the shaft 23 of the electric
machine 8 rotates (and therefore when the primary shaft 15
rotates), the speed of rotation imparted to the carrier shaft 27 by
the mechanical transmission 28 (and therefore by the drive shaft 6
of the heat engine 5) is always lower than the speed of rotation
imparted to the carrier shaft 27 by the mechanical transmissions 30
and 31 (and therefore by the primary shaft 15 integral with the
shaft 23 of the electric machine 8). In this case, the carrier
shaft 27 is rotated by the primary shaft 15 integral with the shaft
23 of the electric machine 8 through one of the two mechanical
transmissions 30 and 31 depending on the direction of rotation of
the primary shaft 15 integral with the shaft 23 of the electric
machine 8.
[0038] When the heat engine 5 is off, i.e. the drive shaft 6 of the
heat engine 5 is stationary, and the shaft 23 of the electric
machine 8 is stationary too, then also the carrier shaft 27 remains
stationary.
[0039] In the aforesaid embodiment there are two different pumps 25
and 26; according to other embodiments not shown, there is a single
pump mounted on the carrier shaft 27 (e.g. in the case where a
single fluid is used for lubrication and implementation), or there
are more than two pumps mounted on the carrier shaft 27.
[0040] In the aforesaid embodiment, the gearbox 10 is a dual-clutch
gearbox; according to other embodiments not shown, the gearbox 10
is a power-assisted single-clutch gearbox, an automatic gearbox or
a manual gearbox. In all these possible embodiments, the mechanical
transmission 28 derives the motion directly from the drive shaft 6
of the heat engine 5.
[0041] In the aforesaid embodiment, the road vehicle 1 has a hybrid
propulsion (i.e. both a thermal propulsion and an electric
propulsion); according to other embodiments not shown, the road
vehicle 1 may have only an electric propulsion and in this case
there would no longer be the heat engine 5, the clutches 16 and 17
and the mechanical transmission 28 (but there would be the two
mechanical transmissions 30 and 31 to rotate the carrier shaft 27
always in the same direction, regardless of the direction of
rotation of the shaft 23 of the electric machine 8).
[0042] The aforesaid road vehicle 1 has several advantages.
[0043] First of all, the aforesaid road vehicle 1 is simple and
inexpensive, particularly starting from an existing transmission
that had not been designed for hybrid applications, since the
general structure of the gearbox 10, and in particular the position
of the pumps 25 and 26 of the gearbox 10, does not change;
basically, starting from an existing transmission that had not been
designed for hybrid applications, the only necessary modifications
are the elongation of the primary shaft 15 and of the carrier shaft
27, the insertion of the freewheel 32 and the insertion of the
mechanical transmissions 30 and 31.
[0044] Moreover, in the aforesaid road vehicle 1, in case of an
electric traction (i.e. when the heat engine 5 is off), the
clutches 17 and 18 can be opened since the pumps 25 and 26 of the
gearbox 10 are rotated through the mechanical transmissions 30 and
31, both in the case of forward motion (where the carrier shaft 27
is rotated through the mechanical transmission 30) and in the case
of reverse motion (where the carrier shaft 27 is rotated through
the mechanical transmission 31).
[0045] Finally, the aforesaid road vehicle 1 is particularly
efficient from the energetical point of view, since when the heat
engine 5 is on, the mechanical energy absorbed by the pumps 25 and
26 of the gearbox 10 is normally taken directly by the drive shaft
6 of the heat engine 5 without any kind of electromechanical
conversion.
* * * * *